Workbook

  • You can run the code in these slides by opening 01-introduction-to-r.R and following along.
  • ALL of the code you see on the screen today is in your workbook.
  • You will learn more if you see the code run for yourself.
    • This is technically an untested hypothesis. Sorry.

Learning Objectives

  • RStudio
  • R Semantics, Structure, Etc.
  • Getting Help
  • Atomic Data Types
  • Vectors

First Steps In R

To Start RStudio

  • Click on the RStudio icon.
  • Open the R Script you would like to run: 01-introduction-to-r.R
  • Sink a very large boat. (Not technically necessary.)


Questions

  • Is anyone NOT using RStudio today?
  • Does anyone need help getting RStudio / R to start?

RStudio: Screenshot 1

RStudio: Screenshot 2

Two ways to run code:

REPL



R Scripts





An Overly Complicated Calculator

  • R is a great calculator.
  • PLEASE tell us know if you can't find this code in the
    01-introduction-to-r.R workbook.
  • Now that you have found it - You try it!
## You can use R as an over-powered calculator.
## Type the following into the REPL console or run them from the
## 01-introduction-to-r.R script.

1 + 1

sqrt(9)             ## sqrt() is a function.

sqrt(1+5+6-3)       ## We can pass values to functions and get results.

Practice: Calculator

This is our first visit from Captain Smith.

## What is the value of (1+2)*(1+1+1) ?

## Write the "equation" here and run it.

Answer:

  • [1] 9

Assignment Operators

NOTE: You should run this code with me.

## The equals sign can be used to assign value to a variable.
a = 1
a

Returns:

  • [1] 1
## But the preferred assignment operator is "<-".
## RStudio Shortcut: [Alt] [-] will insert the R assignment operator.

a <- 1
a

Returns:

  • [1] 1

Practice: Assignment Operator

## Create a variable "sank" and give it a value of "1912".

## Replace this comment with some code.



Correct Answers: (No Peeking!)

  • sank <- 1912
  • sank <- "1912"

Atomic Data Types

Atomic Data Types - Numeric

  • R has extensive support for different types of numbers.
  • R can also handle imaginary numbers and other fun mathematical oddities.
  • Today, we are going to keep it "real".
## Numeric -----------------------------
pi <- 3.14159

## We can confirm this:
typeof(pi)          ## This is a function we will use again.


Returns:

  • [1] "double"

Atomic Data Types - Funny Integers

  • Question: Are you running this code as I do?
  • Best Answer: Yes!
## Integers are funny. They have to be created consciously.
starboard <- 10
typeof(starboard)           ## I told you. This is a useful function.


Returns:

  • [1] "double"
  • Yes, 10 IS an integer but R is treating like a decimal.

Atomic Data Types - Integers

## Integers must be created consciously.
starboard <- as.integer(10)
typeof(starboard)

Returns:

  • [1] "integer"
## We can (double) confirm this:
is.integer(starboard)

Returns:

  • [1] TRUE
  • Question: Why would R have this behavior?
  • Answer: R tries to give your variables the "right" type.

Numerics ARE Safer

## Question: What is the assigned value of port?
port <- as.integer(10)
port

Answer:

  • [1] 10
## Question: What is the assigned value of port?
port <- as.integer(3.14159)
port

Answer:

  • [1] 3
  • The decimal, 3.14159, was coerced to an integer.
  • R floors decimal values. It does NOT round them.

Numerics ARE Safer

## Question: What is the assigned value of port?
port <- 3.3 * 4
port

Answer:

  • [1] 13.2
## Question: What is the assigned value of port?
port <- as.integer(3.3) * 3
port

Answer:

  • [1] 9

Numerics ARE Safer: Discussion

  • Avoid integers unless you KNOW it is an integer.
  • Many programming languages will make integers into integers and then do integer math, even when you don't want it to.
  • R hates you less.
  • Don't look like this guy. Use Numerics.

Atomic Data Types - LOGICAL

## LOGICAL variables are often created in the process of comparing things.
starboard <- 10; port <- 15;

## Question: Is this TRUE or FALSE?
starboard <= port   ## Yeah - It is a little nonsensical.

Answer:

  • [1] TRUE
## Question: Is this TRUE or FALSE?
port = starboard

Answer:

  • NEITHER!!!
  • This is the equivalent of: port <- 10!
  • To compare things, we need slightly different syntax. . . .

Atomic Data Types - LOGICAL

## LOGICAL variables are often created in the process of comparing things.
starboard <- 10; port <- 15;

## THIS IS HOW YOU COMPARE THINGS!
starboard == port

Returns:

  • [1] FALSE
  • Comparison operators: <, >, ==, <=, >=, |, !

Atomic Data Types - CHARACTER

  • Andy likes to call "character" variables "string" vars.
  • He profusely apologizes in advance.
## You can use " or ' to create a character.
## There are subtle differences, mostly if your variable has
## either in it.

## Some character vars:
first_name <- "Captain"
last_name <- "Smith"

## Let's put them together!
paste(first_name, last_name, sep=" ")

Returns:

  • [1] "Captain Smith"
  • We will learn additional functions as we go.

Atomic Data Types - DATES

## POSIX Dates are EASY!
## Like an integer, you have to be explicit.
aft <- as.Date("2015-01-01")

## typeof
typeof(aft)         ## typeof may return something you don't expect.

Returns:

  • [1] "double"
  • Stored internally as a number.
## Kinda looks like a character var.
aft

Returns:

  • [1] "2015-01-01"
  • But it LOOKS like a date when we look at it.

Practice: Atomic Data Types

## 1: Create an variable called "my_age" and then
##    assign it an integer equal to your age.

## 2: Using the following code, which is bigger (later)? a_day or today?

## This creates two date vars.
a_day <- as.Date('2015-06-30')
today <- Sys.Date()

## Use this space to compare a_day to today.
##

Example Answers:

  • my_age <- 36
  • a_day < today which returns: [1] TRUE
  • There are, obviously, other possible answers.

Vectors

Vectors

  • Vectors are a 1-dimensional data set in R.
  • They have two important attributes:
    • Data Type (can be ANY)
    • Length
yard_arm <- c(1,2,3,4,5)      ## The Titanic's maiden voyage
                              ## lasted for five days.
yard_arm

Returns:

  • [1] 1 2 3 4 5
  • The "atomic" variables we created earlier? Just vectors with length 1.

Vectors - Length

## The variable yard_arm has five distinct values in it.
length(yard_arm)

Returns:

  • [1] 5
## This variable only has one value.
starboard <- 1
length(starboard)

Returns:

  • [1] 1

Vectors - Indexing

  • Sometimes, we only want to work with part of a vector.
## Returns the THIRD value stored in yard_arm.
yard_arm[3]         ## The square brackets are important.
                    ## They let us reference and filter
                    ## values in the object.

Returns:

  • [1] 3
## Returns ALL values in yard_arm with a value greater than 2.
yard_arm[ yard_arm>2 ]        ## Easy way to filter data.

Returns:

  • [1] 3 4 5

Arithmetic on Vectors

  • Arithmetic is done on all members of the vector.
## We can do math on vectors.
starboard <- c(25,30,40,45,50)
port <- c(90,70,50,30,10)

starboard + port

Returns:

  • [1] 115 100 90 75 60
## We can do math on vectors.
starboard <- c(25,30,40,45,50)
port <- 3

starboard * port

Returns:

  • [1] 75 90 120 135 150

Operating on Vectors

  • Many functions will roll up the values.
## We can do math on vectors.
starboard <- c(25,30,40,45,50)

mean(starboard)

Returns:

  • [1] 38
## We can do math on vectors.
starboard <- c(25,30,40,45,50)

sd(starboard)

Returns:

  • [1] 10.36822

Operating on Vectors

  • But not all.
## We can do math on vectors.
starboard <- c(25.1,389.776,43.6,41.3,57.56)

round(starboard,1)

Returns:

  • [1] 25.1 389.8 43.6 41.3 57.6

Discussion:

  • When using functions on vectors you MUST know what it is doing.
  • Or you may get unexpected results.

Practice: Vectors

  • Last practice before we break.
## 1: Create an vector, with a length of 4. Put the years
##    you went to highschool into this vector.
##    "Numeric" integers are fine for this. You don't need dates.
##    If you need help, try this:
##    ?c

## 2: Use an index and a greater than or less than boolean operator
##    to return the last three years you went to highschool.

## 3: Run typeof on your new highschool years variable.
##    What is the output.
##    Does it surprise you?

## 4: What was the "average" year you went to highschool?
##    Yes. This is a completely meaningless number. Sorry.
  • Example Answers on next slide.

Example Answers:

  • hs_years <- c(1994,1995,1996,1997)
  • hs_years[ hs_years>1994 ] which returns: [1] TRUE
  • typeof(hs_years)
  • mean(hs_years)

Quick Recap

  • RStudio
  • R Semantics, Structure, Etc.
  • Getting Help
  • Atomic Data Types
  • Vectors

Questions?